n -digit numbers are formed using only three digits 2 ,   5 and 7 . The smallest value of n for which…

n-digit numbers are formed using only three digits 2, 5 and 7. The smallest value of n for which 900 such distinct numbers can be formed is :
  1. 9
  2. 7
  3. 8
  4. 6

Solution

n- digit number are formed using only three digits 2, 5 and 7 with repetition =3n.

Since, 36<900 and 37>900

So, n=7.

Asked in: JEE Main 2018 (15 Apr)

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